Preionizing arrangement for transversely excited lasers

In a transversely excited gas laser having a laser discharge channel and a pair of opposed main discharge electrodes longitudinally disposed in said channel in transversely spaced relation, the improvement comprising:

• preionizing electrode means in said channel defining an electrical current flow path between said main discharge electrodes, said preionizing electrode means including a plurality of longitudinally aligned and longitudinally spaced apart pairs of semiconductive plates, each said plate of said pair of plates being in electrical current conducting relation with one of said main electrodes and defining therewith a longitudinally extending plate-electrode discharge gap, said plates of each said pair of plates being disposed at an angle to one another and together defining a longitudinally extending interplate discharge gap;
• said electrode plates being formed of a semiconductive material characterized by a relatively high impedance at relatively low voltages and a rapidly decreasing impedance at increasing voltages beyond a breakdown voltage such that upon application of a high energy, high voltage electrical pulse to said main electrodes and said preionizing electrode means, the electrical impedance of said preionizing electrode means drops below the impedance of lasing material in said channel whereby electrical current initially flows through said preionizing electrode plates and produces a longitudinal, filamentary discharge along each said gap, which discharges serve to precondition said lasing material within said channel.